In fluorescence observation performed by using a microscope, there is a known microscope system with which the black balance is corrected in order to improve the distinction between a specimen and portions in which the specimen does not exit (for example, see Patent Literature 1). With this microscope system, in accordance with the distance between the peak of low-luminance displacement points and the peak of high-luminance displacement points in a luminance histogram of an image, it is judged whether or not to remove a lower luminance side thereof, which corresponds to a background portion, and processing is performed accordingly.
For example, in FISH (Fluorescence In Situ Hybridization) observation, a detection target, namely, EML4-ALK, which is a gene responsible for lung cancer, is tagged with green (FITC) and red (TexRed) probes, and the presence/absence of translocations in the EML4-ALK gene is checked based on the proximity or separation between green signals and red signals. Therefore, it is not possible to improve the clarity of the observation subject by removing the lower luminance side that corresponds to the background portion, as in the case of Japanese Unexamined Patent Application, Publication No. 2010-98719, and, ideally, it is necessary to remove not only the background portion but also all signals other than relevant signals.
In particular, because an operator who performs FISH observation has to check signals for more than several hundred locations per day, it is not efficient for the operator to manually perform image manipulation each time a still-image is acquired.